1. Field of the Invention
This invention relates to a novel separation membrane which is suitable for microfiltration, ultrafiltration, dialysis and in general for concentration of aqueous solutions, and which is also suitable for separation of materials.
2. Description of the Prior Art
Methods involving separating materials by employing membranes have recently been drawing great attention in various fields by technology and industry, including waste water disposal, food industry and medical applications. These methods include microfiltration, ultrafiltration and dialysis, and are selectively employed to suit the particle sizes of materials floating, dispersed or dissolved in an aqueous medium. While different types of membranes are, of course, used for different purposes of separation, all the membranes are required to have a high rate of permeation to an aqueous medium, to be highly capable of removing the materials floating, dispersed or dissolved therein, and to have a high degree of mechanical strength and chemical resistance.
Many separation membranes are known such as those disclosed, for example, in U.S. Pat. Nos. 3,546,142; 3,896,061 and 4,118,439, but few of them fully satisfy the requirements mentioned. Moreover, it has been difficult to manufacture different types of membranes for different applications from one and the same material by one and the same process.